Designed fabrication of lightweight SiC(Hf, rGO) bulk composites derived from Hafnium-modified precursors for hypersonic vehicle components

Demand for SiC-based polymer-derived ceramics (PDCs) employed as hypersonic vehicle components with light weight, high strength, excellent high-temperature/ablation resistance is increasingly urgent. Herein, bulk SiC(Hf, rGO) nanocomposite PDCs were fabricated via re-pyrolyzing ball-milling blends of unique SiC(Hf, rGO)p/polyhafniumcarbosilane-vinyltriethoxysilane-graphene oxide (PHVG). Highly cross-linked PHVG can effectively optimize compact formability and improve ceramic yield. In-situ formed HfO2 embedded in ceramic network toughens microstructure, while interfacial HfOSi increases structure disorder to improve high-temperature properties. As demonstrated, SiC(Hf, rGO) modified by 3 wt.% Hf and re-pyrolyzed at 1300 °C possess good mechanical performances including hardness (5.83 GPa), fracture toughness (4.29 MPa·m1/2), compressive strength (181.83 MPa) and flexural strength (46.55 MPa). More interestingly, self-healing HfO2(HfSiO4)/SiO2 protective layer emerging during 20 min surface ablation test at 1300 °C, timely covers defects and avoids destructive structure, thus retains stable structure and mechanical properties of specimens. Such nanocomposites can promote uses in thermal protection systems (TPS) for hypersonic vehicles against extreme high-temperature environments.